Temperature and frequency dependent electrical properties of NiCuZn ferrite with CuO-rich grain boundary segregation

Polycrystalline Ni0.9−yCuyZn0.1Fe1.98O4−δ (y = 0, 0.1 and 0.2) powder was synthesized by conventional solid-state reaction method. X-ray diffraction analysis confirmed single phase cubic spinel phase formation in the calcined powders. An additional phase was observed predominantly after sintering of y = 0.2 compound. The extra phase in the sintered sample is due to the formation of CuO-rich segregation along the grain boundary, which is confirmed by high resolution scanning electron microscopy, X-ray diffraction and energy dispersive X-ray spectroscopy analysis. In order to understand the temperature and frequency dependent electrical properties of segregated ferrite, detailed impedance spectra was investigated on Ni0.7Cu0.2Zn0.1Fe1.98O4−δ in the frequency range of 1 kHz-1 MHz and temperature range of 30-250 °C.